Method
Real-money market-based pricing offers a new, exciting, alternative set of state-level odds to analyze.
In 2016, with the success of the PredictIt.org marketplace, we began our market-based analysis of the Electoral College and the Senate.
From individual contract pricing, we calculate each candidate's implied probability of winning, after adjusting for the 10% commission on winning trades.
We determine the probability for the Democratic candidate and the Republican candidate and use these individual race probabilities to calculate the odds for every possible combination of outcomes
and calculate each party's odds of winning.

Currently, Republicans hold a 51-49 edge.
This year there are 35 Senate seats which are up for election, 26 will be defended by Democrats and 9 by Republicans; 42 Republicans and 23 Democrats are not up for re-election.
Republicans need to win 9 seats to retain control of the Senate; Democrats need to win 28 seats to win control.
With 35 seats, there are 2^35, over 34 billion, possible combinations of outcomes.
From the individual race probabilities, we calculate the odds for every possible combination of outcomes and calculate each party's odds of winning.
Here is the current probability distribution for our market-based analysis:

Here is the market-based projection of the number of Senate seats for each party:

Currently, our market-based analysis analysis indicates that the odds the Democrats will take control of the Senate are very slim.